Comment 2 for bug 1557173

StacktraceTop:
 pa_cvolume_set (a=a@entry=0x7ffceef814d0, channels=<optimized out>, v=<optimized out>) at pulse/volume.c:74
 transport_speaker_gain_changed_cb (y=<optimized out>, t=<optimized out>, u=0xc170f0) at modules/bluetooth/module-bluez5-device.c:2369
 pa_hook_fire (hook=0xc705d8, data=data@entry=0xc49d50) at pulsecore/hook-list.c:104
 rfcomm_io_callback (io=<optimized out>, e=<optimized out>, fd=22, events=<optimized out>, userdata=0xc49d50) at modules/bluetooth/backend-native.c:244
 dispatch_pollfds (m=0xbd2170) at pulse/mainloop.c:655